


Curiosity

by HostisHumaniGeneris



Category: Prototype (Video Games)
Genre: Anal Sex, M/M, Oral Sex, Plot What Plot/Porn Without Plot, Rough Sex, Tentacle Sex, Transformation
Language: English
Status: Completed
Published: 2017-12-03
Updated: 2017-12-03
Packaged: 2019-02-10 06:14:03
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,136
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12905856
Author URL: https://archiveofourown.org/users/HostisHumaniGeneris/pseuds/HostisHumaniGeneris
Summary: Alex Mercer isn't human, but is interested in exploring a wide range of human... activities.  Robert Cross is begrudgingly accommodating.





	Curiosity

**Author's Note:**

> Written for the more-or-less defunct Prototype Kink Meme, in response to the prompt:  
> "Does anybody else just sort of wander in here every couple of years or so to re-read old favorites and check for new stuff? Is that just me?
> 
> Also, can somebody write something where Alex is blatantly inhuman? Like, tentacles and strange behavior and the like...preferably with Cross. Pretty please?"
> 
> Dunno why it took me a year to get to posting it here.

Alex Mercer was curious.

It started off simple enough. They fucked. Not that often, but they’d meet up to share information, and that eventually led to him shoving Mercer against a wall or Mercer pinning him down and they’d fuck. Which one was on top varied; they didn’t agree to take turns or anything, sometimes he’d end up shoving roughly into Mercer, up against a wall, sometimes he’d end up flat on his back, legs hitched over Mercer’s shoulders. Maybe a handjob afterward if the receiving partner didn’t get off. Mercer’d show up, they’d fuck, Mercer’d leave. 

Cross told himself it was a way to work off tension.

Since the death of Randall, it was tense. The upper echelons were busy covering their asses and assigning blame, the people below him were looking to him for guidance, he had no clear idea on how to proceed. Blackwatch’s job was a necessary evil, always had been. Learning that they had been behind most of the messes they had to clean up didn’t change that they were the ones to clean up the messes. And Mercer, as always, remained an annoying loose end. He’d killed countless Blackwatch troops, Marines, and civilians, he was too dangerous to just let go. He was also too powerful to kill. He killed Greene and broke the back of the infection; something Blackwatch failed at. He killed Randall. He saved Manhattan.

Hearing Mercer groan and grunt when he got fucked up the ass by Cross didn’t make anything easier. But it worked off tension. 

So of course, Mercer had to fuck it up.

It started off small. First, their encounters increased in frequency. That took up more of Cross’s time, and also increased the risk of being caught. Aiding and abetting a federal fugitive on Mercer’s level was enough to get him locked in a stockade for the rest of his life or executed. Fucking the viral freak? The best case scenario was a 5.56 millimeter to the back of the head and an unmarked grave. Worse scenarios involved ending up a test subject. But it was hard to voice that concern to Mercer in between panting and groaning.

Mercer developed a fascination with oral, giving and receiving. Cross hadn’t minded at first, it was faster and took less preparation. Mercer was a great cocksucker. The taste of his skin was wrong… Cross never tasted more than that, they had settled on Mercer never cumming inside him. It was fine. Until one night when he was on his knees Mercer held his head down, denying him air until he panicked, pounded Mercer’s bare thigh until he finally took the hint and released him. Cross was panting and gasping while Mercer looked confused until he sank down and undid Cross’s fly. Took Cross’s entire length for way too long; grabbed his hips and forced his partner down his throat. Mercer departed with Cross’s cum on his face. 

That should’ve been the end of it.

It wasn’t.

Mercer came back a few days later and Cross had attempted set ground rules. Mercer had shrugged and agreed. On occasion, they’d try something new, usually at Mercer’s insistence. Handcuffs, tickling, blindfolds; he’d come up with a fetish that’d disappear as soon as it appeared. Not exactly Cross’s cup of tea, but if it ended with him getting off, that was fine.

Then one night Mercer shoved him down and pinned him, letting Cross struggle fruitlessly against his superior strength. He did that sometimes, usually when he wanted to top. Cross was already semi-hard when Mercer undid his fly and began stroking his cock. That got him fully erect. Then tendrils began to creep out of Mercer’s skin and he slithered. Cross had become used to that; it was how the man “got out” of his clothes, but it went on slightly too long, wasn’t limited to just the leather jacket and the hoodie.

Cross wasn’t interested in women. He did have a few girlfriends during his high school and college days, but they did nothing for him. So, when the slithering ended and Mercer was a petite brunette with perky tits, it came as something of a shock. It was purely physical, when Mercer impaled himself… herself… on his cock and rode him. Something tight and warm and wet against his cock did prompt a response, even if Cross himself wasn’t nearly as enthusiastic as Mercer was. No conversation when it was over, Cross just grabbed Mercer, again looking like Mercer, by the arm and told him to never do that again.

He seemed slightly disappointed, but nodded and left.

It was distracting, for lack of a better word, over the next few days. When they just fucked, that was it, just a way to relieve tension. No need to think about how the man you’re fucking wasn’t human. That he could change _everything_ on the fly. That his list of curiosities and interests dwarfed Cross’s. Mercer shifting who he was on top of him? Cross couldn’t ignore it.

Who was the woman? Part of him was sickened by the idea he fucked someone Mercer killed and was using in a bit of roleplay during sex, until he remembered that was the exact same situation as fucking Mercer when he was Mercer. That didn’t make the woman _better_ , it just made the concept of sex with Mercer _worse_.

Was Mercer interested in women? He seemed to like the female form, playing with his breasts while bouncing on Cross. That raised the question of whether or not he sought female companionship. Were they exclusive? Cross hadn’t exactly put any thought into that before. The man had some pretty wide interests, and maybe he’d find someone willing to indulge them. They never actually discussed their relationship much, and Cross had a hard time when he tried figuring out why he started fucking a plague monster.

Mercer was a sentient pile of virus material in human shape. He was a wanted fugitive. He had killed Cross’s comrades and commanders. Cross almost killed him. Cross was still working for a unit that wanted Mercer dead and that Mercer wanted dead. Yeah, Mercer was a good fuck, a great fuck actually, so long as he wasn’t doing something completely fucked up. But there were plenty of outlets for that particular urge. Safer ones. So why did they have sex?

He planned on actually getting an answer to that question out of Mercer the next time they saw one another.

That didn’t happen. He just grabbed Mercer by the hair with both hands and drove into him hard. He was a lot rougher than usual, he chalked it up to that previous time getting more under his skin than he liked. Mercer should not have pulled that without asking if he was okay with it. Besides, Mercer could take it.

Mercer could take a lot.

To Cross’s chagrin.

That encounter seemed to lead to Mercer getting a fascination with pain. Not ‘bent over a knee and spanked for being a bad boy’, he wanted to be hurt. Asked Cross to punch him. Hard. He indulged him, and for whatever reason Mercer’s face swelled and reddened like anyone’s would; didn’t heal or anything. Asked for another, he refused. Mercer goaded him. Made a jab about a convoy that got torn apart by infected earlier that week. That set something off. Cross punched him until the knuckles of both hands were bloody and then fucked him raw while strangling him. Mercer grinned through a mouthful of broken teeth, that bloodied face shifting back to normal a minute after he had cum. 

Cross wasn’t sure what sickened him more, that Alex got off on it or that he did. 

The next few time was less violent, but he still was falling for it. Mercer’d give a smug fucking look that Cross just _had_ to wipe off his goddamn face. Then the encounter was over and Mercer was back to normal, that neutral expression he usually wore. It eventually dawned on Cross to ask him why he wanted to be hurt.

“You seemed stressed.” He had said with a shrug. “Figured you needed an outlet.”

Yeah. He was stressed.

That inhuman fuck was what was stressing him.

A few days passed before Cross started to get agitated.

Mercer was usually the one to come to him. 

But he didn’t.

Should’ve been a relief.

But it wasn’t.

It was a little over a week before Cross started to put some effort into tracking him down. Just to talk. At least, that was the plan. There were a few leads. Blackwatch had a few theories, then there was Ragland. He should’ve just been resting during downtime, not playing detective.

But he did.

A few strategically worded inquiries, and he found himself in civilian clothes, standing in the middle of an abandoned apartment in Manhattan. It was unadorned, except for an old mattress in the corner and a bunch of papers on two walls. The first was photos, newspaper clippings, classified briefings, maps, most were on Blackwatch and Gentek. Lines were drawn from article to photo, color coded notes were made on maps and papers. The other wall had random pictures; scenes from travel magazines, pictures of central park before the outbreak, printouts of porn featuring flexible and not-shy men and women, and two picture frames. One held an NYU student I.D. belonging to Dana Mercer, the other was a picture of him, shortly after Two Bluff, taken from some Blackwatch file that went missing. This was a goldmine of intel about Mercer’s thought processes and plans, and Cross focused on it way too long.

He was interrupted when something coiled around his ankle and dragged him off his feet; something else grabbed him and hoisted him up before he hit the ground. He kicked and thrashed before being unceremoniously dumped on the mattress. 

Mercer was standing over him.

He looked down at his ankle; a black tentacle ran from it to Mercer. More shot out, and soon Cross’s wrists were lashed together and his other leg held down. 

“Been a while.”

Cross was about to tell Mercer to let him go when something slithered up his neck, across his cheek. Cross clamped his mouth shut the instant before the tentacle ran over his lips. Mercer chuckled and dropped to a crouch. 

“I know that the things I’m interested in, you might not like.” Mercer growled into his ear. “Just say the word, and I’ll stop.”

There was something about that tone, sounded less like an offer and more like a challenge. Smug prick. Cross growled in annoyance.

“Don’t worry, I think you’ll like what we’re going to do tonight.” Mercer nodded. “I promise it’ll feel good, at least.”

Cross said nothing. Out of his peripheral vision, the tentacle that had run across his face slid out of view.

Mercer shrugged, and planted his hand against Cross’s throat, then ran it down, past Cross’s chest, over his abdomen, and right on his crotch. He was already hard when Mercer rubbed his cock through the layers of denim and cotton covering it. He’d been hard since Mercer grabbed him.

Mercer leaned in close and kissed him, pressing their lips together. Somewhere in the back of his mind, Cross noted that was the first time they did that. Fucking, they did a lot of. Kissing just wasn’t something they did. Mercer pulled back and looked him over. “I’ve missed you.”

“Then why…” Cross stopped. He wasn’t going to give the freak the satisfaction of hearing him ask why they hadn’t fucked in a while.

Of course, Mercer could assume what he was going to ask. “Wanted to see if you’d come to me.”

“I…” _God damn him_.

“You enjoy our time together.” Mercer offered. “I do too.”

He wanted to scream at Mercer that no, it was just a matter of getting off. He could’ve found anyone else to fuck, it wasn’t just Mercer. But… it had been just Mercer. Hadn’t been anyone else. When Mercer stopped coming around, rather than counting his blessings and finding a new fuck, he decided to hunt for Mercer with more urgency than he’d been hunting for Mercer as Blackwatch’s pointman. For all of the fact that it was sick, crazy, wrong for him to be fucking that thing, here he was, rock hard and waiting. “So you got me. What now?”

Mercer smiled. 

Cross was sure part of him should’ve been nervous about that. But he was excited actually. Really, mostly just wondering about what Mercer had in store for him.

Robert Cross was curious.

Mercer gripped the front of Cross’s shirt in on hand and ripped. When he opened his mouth to protest a tentacle found its way in. Mercer looked in the torn fabric in his hand and chuckled. “Don’t worry. I’ll get you something to wear when we’re done.”

Cross mumbled two syllables around the limb in his mouth. It tasted bitter. 

Mercer let the fabric fall to the floor and his right arm shifted into wicked looking claws. Cross’s heart sped up, but he didn’t let his face betray any emotion. Mercer was trying to agitate him, and there was no doubt Mercer could kill him if he wanted, but Cross was sure he didn’t want to hurt him. Just provoke a reaction. 

Mercer held still for an agonizingly long time before going to work, slowly shredding Cross’s jeans and underwear without even nicking his skin. Mercer was being cautious even if he had been trying to unnerve Cross, carefully cutting away from the skin until Cross was naked save for his shoes, socks, and some random strips of denim on his legs. The claws receded and his hand was normal by the time those fingers wrapped around Cross’s cock. 

Mercer jerked his hand up and down for a moment, before letting go. He looked preoccupied. Just as Cross made a curious sound around the tentacle in his mouth, he felt tendrils winding up his legs. They slid across his stomach and chest. One slithered its way along his inner thigh and traveled up, snaking around his cock. It was warm and slick and pulsed slightly. 

“Trying something new tonight.” Mercer explained.

It should’ve bugged him. Now, more than ever, Mercer was incorporating just how much of an inhuman monster he was in their sex life. But god damn it, he was interested in seeing where exactly this would go.  
When another tendril crept along the back of his thigh and traveled to his ass It was narrow and slick and slid in easily. Cross shuddered as it ran along inside him, twitching and pulsing curiously. Cross let out a muted groan as it grew thicker, it’s movements more targeted.

Mercer looked down intently as the tentacles played with Cross, inside and out. He was getting close, so very close.

Painfully close.

Then the tendrils stopped. 

He let out a confused sound around the tendril in his mouth, which must’ve sounded incredibly pathetic, as Mercer continued to loom over him. Confusion turned to anger when he saw that smug fucking grin on Mercer’s face.

He was so close, damnit! And Mercer just stopped. He swore into the tendril gagging him, voice raising a half-octave when the tendrils started again.

Mercer was a sadistic fucking monster. Over and over, he drove Cross straight to the edge, only to stop. It was sick and disgusting and Cross fucking hated nothing more than Mercer every time the tendrils stopped. But when he started again…

Cross hadn’t been paying attention when Mercer’s clothes dissolved in a flurry of tendrils, didn’t notice the tendrils winding around Mercer, inside Mercer. Beneath the blinding frustration and need, it took him entirely too long to notice Mercer had been jerking himself watching Cross writhe and moan. When he finally did, after an extended period of no stimulation, Mercer began to crawl on top of him. The tendril around his cock unwound itself from him.

“Having fun?”

Cross said nothing, not even an annoyed grunt. Just stared. Mercer had to have had his fun, right? He wasn’t going to keep him on the edge like this, right?

That was confirmed when Mercer lined himself up and impaled himself on Cross’s cock. Tendrils lashed the two together, ran over their bodies. He lifted himself up, then down. And again, and again. Mercer screwed his eyes shut as he rode Cross, moaning and growling and making less describable sounds.

The tendrils holding him loosened as they fucked, made sense, given Mercer’s mind was elsewhere. Cross managed to slip one arm free of the tendrils binding his wrist, and there was enough slack now that his other arm had full range of motion. He pulled the one in his mouth out and spat off to the side, running his tongue along his teeth and spitting again.

He wrapped a hand around the back of Mercer’s neck and pulled him down, almost face to face, started bucking his hips. Mercer growled, clawing at the mattress.

That just prompted Cross to buck harder.

Something warm and wet and sticky splashed across Cross’s belly in spurts, punctuated by Mercer shouting something unintelligible and every muscle in his body going slack. Jesus Christ, he weighed a ton. The tentacle down Mercer’s throat retracted and he muttered “That was great.”

Cross continued thrusting awkwardly against the dead weight on top of him for only a brief few seconds before cumming hard, exploding inside Mercer. Between the dry spell from the last time they fucked, and the amount of time Mercer had taken driving him to the edge and backing off, it was the most intense orgasm Cross could recall.

It left him breathless, his limbs feeling like rubber. 

Mercer got to his feet and stretched. A few more seconds of thrashing tendrils and he was fully dressed, like they hadn’t just fucked one another’s’ brains out. Cross laid there, growing soft and panting. He was exhausted. 

“That was fun.” Mercer said, nodding. He then excused himself to get replacement clothes for Cross.

Yeah, fun. Fucking bizarre, intense, inexplicable. But fun, too. He was completely fucking spent, but it was great. That was why he kept coming to Mercer, beyond all the weird shit, he was the best Cross had ever had. Hell, going by today, the weird shit was amazing, too. There was nothing quite like this.

He could’ve thought about how to introduce this evidence to Blackwatch. How to extricate himself from this situation; things hadn’t changed, he was still fucking something he was obligated to destroy, and who in general wanted nothing but the death of everything Cross fought for. But all he could think about was what to do when Mercer came back.


End file.
